Where does the sand on the beach come from?

Where does the sand on the beach come from? – Sly M., age 6, Cambridge, Massachusetts, United States

There is much more to the sand than the beach that we don’t know. It offers stories about the land and an epic journey to the sea. This is because the mountain ended its life as sand on the beach.

Over time, the mountains will erode. The mud, sand, gravel and boulders that pour are carried away by the currents and then combine to form rivers. As they flow into the ocean, all of this sediment is ground up and buried in a natural version of rock glass.

The boulders are broken into small pieces, so most of what reaches the sea is mud. These mud and clay particles are too small to be seen with the naked eye. However, you can see the grains of sand which are just larger pieces of rock.

If you go to the beach after this, try grabbing a handful of sand and watch carefully. Are the grains all the same color or the colors of the rainbow? Are they jagged and angular or smooth and round?

The color of the sand can be different because they come from different minerals, such as khaki color feldspar, quartz smoky white, olivine green, o basal Black. The color scheme of the sandy beach indicates the type of rock that produced it.

The shape of the sand grains also provides clues to their origin. Angular grains of the same type of sand did not travel to the fine, rounded grains. On the other hand, weak rocks break down in mud faster than hard rocks, so sand tends to be made up of harder types that break down more slowly.

About a tenth of the sediment that reaches the sea is made up of sand. These particles are between about half a millimeter and 2 millimeters in size, roughly the thickness of a coin. These particles are large enough not to flow directly into the deep ocean.

However, the beach is only a temporary stop for the sand. Big waves push it offshore and smaller waves push it along the coast. Therefore, maintaining a sandy beach is very important to keeping it sandy.

However, many beaches lack sand right now. Many dams trap sand that flows into rivers and accumulate it in reservoirs. Overall, human activities have reduced by approx half the amount of sand which should end up on beaches all over the world.

Since humans cannot stop the waves, the sand on the beach is washed away and not replenished. As a result, the coast is eroded. This means that many of the world’s beaches are slowly but surely shrinking.

So next time you dig for beach sand, think about the epic journey it takes to get sand under your feet. Take a moment to think about where the sand came from and where it went.

Do you have a question you would like to develop for an expert? Ask a parent or elderly person for help by sending us your questions.
When submitting a request, make sure you have entered your short name, age and city of residence. You can:

Zalfa Imani Trijatna of the University of Indonesia translated this article from English.